At http://search.cpan.org/~michielb/DBD-mysql-4.043/lib/DBD/mysql.pm#SYNOPSIS it shows

 my $dsn = "DBI:mysql:database=$database;host=$hostname;port=$port";
 my $dbh = DBI->connect($dsn, $user, $password);
[download]

Note that compared to your example it shows the database specification coming before host with the ":" before database and ";" before host.